Let's talk about how to classify spell types and see if that reveals any meaningful data about the game balance and spell selection (v1.0.5)...
First we have what I would call Defensive Spells:
1) Armor of the Sun - Passive defense / weak to inexpensive attacks (of which there are few).
2) Heavenly Dome - Active 360 degree defense + healing / expensive.
3) Shield of Light - Active forward defense + reflected damage / many weaknesses but cheap.
This is a good mix. While each spell offers the same basic function (block damage) they each provide very different utility. Once properly tuned (and bugs fixed) we should see an even distribution of these spells being used by players depending on their preferences.
Area Control Spells:
1) Devils Twins - blocks access + threat of being player + reflects damage + cheap / ?
2) Stone Demon - Classic turret...blocks access + threatens area within LOS + damage / expensive
3) Acid Cloud - Soft area denial + can push players out of an area / easy to counter & avoid
1) Petrifying Prison
Only one stun spell, so no comparison to be made.
1) Teleport - Can't be unequipped.
2) Chaos Leap - No-look teleport + escape trap + random destination / random destination can also be a liability.
Despite not being able to unequip Teleport, Chaos leap does offer a different enough utility that it is a value-add to the vanilla Teleport. What if you had to pick between the two though? In the future, maybe you can swap out Teleport for one other mobility spell...
Now, finally, Damage Spells:
1) Lightning Strike - 0.8 damage/mana ratio, sniper + no cost on cancel
2) Hail of Death - 0.8 damage/mana ratio, mini-gun
3) Devils Spit - 0.72 damage/mana ratio, workhorse + skill shots
4) Electric Fist - 1.6 damage/mana ratio, shotgun + ricochet + charge to extend effective range
5) Blazing Meteor - 0.63 damage/mana ratio, ???
6) Flaming Phoenix - 1.4 damage/mana ratio, heat seeking rocket / slow
7) Soil Spikes - 0.56 damage/mana ratio, no aim targeting / delayed damage
Here is where we run into some problems. There is a lot of overlap or lack of utility and the end result is that some of these spells end up being strictly superior to the others.
Lightning Strike has a ton of utility. It is ostensibly the long-range sniper weapon, but it is equally as good at close range. It can bait defense spending at no cost, can be canceled at will and has instantaneous high damage. It can also kill Twins with no reflected damage, can one-shot a Demon and has a pretty high damage to mana cost ratio. For liabilities there isn't much: it can be weak against habitual teleporters and is not cost effective against Armor.
One weapon you might choose instead of Lightning Strike is Hail of Death because it is most effective against the one spell Lightning is weak against: Armor. Hail also has a lot of additional utility: it is very cost effective because you can turn it off or redirect the hose as soon as your opponent teleports. It is the cheapest way to kill Twins and also does not reflect damage (I think?) After the 1.0.5 accuracy buff it is good out to medium range, which covers most encounters. Its liabilities are limited and mostly covered by Lightning Strike.
There aren't many situations left that aren't covered by Hail and Lightning, though Devils Spit can still prove very useful because of its unique ability to do trick shots (curve around obstacles, near-miss fake-outs that curve in, hitting players from above/behind/etc.) In addition, Spit also has many of the same qualities that make Lightning or Hail so effective: Good at any range, good rate of fire, good damage/cost ratio, good against Twins/Demon, etc.
Now we get into the spells that can't compete on utility:
Electric Fist has one utility that isn't redundant with another spell: ricochet, which turns out isn't that useful anyway. Its close-range attack is similar in function but inferior to Hail and its charged attack is similar but inferior to Lightning. You can tune the damage/cost to balance it, but it would still be redundant in its application. To make this spell useful, I would really look for ways to make the ricochet ability a must-have utility.
Blazing Meteor also has a redundancy problem. It's basically the same as Devils Spit except big, slow, poor damage/cost and no curving. In what situation does Meteor shine where other spells do not? I think one way to give this spell a unique utility is to dramatically play up the splash damage...perhaps have it explode into smaller chunks on impact like a cluster bomb to feed this back better. Then players might choose it to do damage around corners or maybe even hit multiple targets at once (nearby twins, demons, player, etc).
Flaming Phoenix's unique utility is its homing ability, but this is too easily countered (break LOS, throw up shield/dome/armor). Without the homing, it's basically another Meteor (which itself is already redundant). Tuning speed/cost/damage may balance it, but again this isn't making it independently useful. About the only thing I can think of here is to make the bird much better at pathfinding so you must either use a shield or outrun it until it dissipates on its own. A spell that forces the other player to keep burning Mana on teleport could be quite useful.
Finally Soil Spikes. Terrible damage/cost, so no one is ever going to choose this simply to do damage. What are its utilities then? It can be cast without aiming, is effective at any range, can penetrate Dome and Shield. It's main liability is that it has a warmup that can be dodged (quite easily, in fact). If you tune the warmup time down and/or improve the damage/cost it becomes more and more useful as a skill-less sniper weapon (and would eventually become strictly superior to Lightning). Off the top of my head I'm not sure what would be a good way to fix this one.
Thanks for reading! That was a long one!
tl;dr - Some attack spells aren't very useful.